Principle And Control Techology Of Bearingless Brushless DC Motors

A brushless DC motor is a new type of motor that gets much popularity in the past few years. It combines the characteristics of AC motor and DC motor.Therefore,it has excellent timing capability,high efficiency,simple configuration,reliable operation,and can be controlled and maintained easily.The bearingless brushless DC motor(BLDCM) is an innovational type of motor,which has all excellence of magnetic hearings.As it is widely used in field of biologic engineering,aeronautics and astronautics,high technology energy resources,semiconductor manufacturing industries,food processing industries,medicine and sanitation industries,the research on BLDCM has received a lot of attention.The dissertation focuses on the fundamental theory and experiments of BLDCM including mathematic models,flux oriented controller,speed sensorless technology and the digital control system design.The detail contents are as follows:Firstly,the principle of radial suspension force is expounded.The mathematic models of radial suspension forces and rotation part of the BLDCM are deduced.In order to realize the decoupling control of torque and radial suspension forces for BLDCM,control system based on rotor flux oriented control is designed.The control system is simulated with Matlab/Simulink toolbox.The simulation results have shown that rotor can suspend steadily,torque and radial suspension subsystems can be controlled independently,the control method is valid and the whole control system has fine static and dynamic performance.Secondly,according to an Extended Kahnan Filter(EKF),a method for estimating the speed of sensorless bearingless brushless DC motor drives is proposed.The mathematic models of EKF are deduced,and the speed sensorless flux oriented control system of BLDCM is constructed. Using Matlab/Simulink toolbox,the simulation model is established.It can be seen that the control system has good performance by simulation.Finally,based on the principle of rotor flux oriented control,the digital control system is designed using TMS320F2812A of TI Corporation,and the flowcharts of each functional block are presented.Based on the prototype of BLDCM,the digital control system is debugged and optimized.The experimental rig of digital control system is set up and is used to validate control strategy.